The present invention relates, to a warning display device in an electric shutter for cameras for perfection of making confirmations as to whether controlled time of exposure of the camera is within a controllable range against the brightness of the object, as well as giving warning, when such range is surpassed, and making its indication electrically.
In the prior art, one of the systems for a warning indicating device for correct exposure of the camera, has been proposed as one in which two kinds of pulses are generated: one with a pulse width in inverse proportion to the brightness of the object (corresponding to the effective time of exposure), and another with a certain width of time as reference, simultaneously, and by comparing the two, an alarm indication or indication of correct time of exposure is displayed on the camera. This known system permits a precise measurement in a wider range, when compared with the other known system giving warning by effectuating direct measurement of resistance value of photoconductive elements. However, its circuit composition becomes very complex and, consequently, its elevated cost cannot be avoided.